Electron discharge device



PY] 20, 1948. H. G. ADERSN 2,439,786 V I ELECTRON DISCHARGE DEVICE Fi-led Nov. 7, 1944 :iin

Patented Apr. 20, 1948 ELECTRON DIS CHARGE DEVICE Homer G. Anderson, Waban, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application November '7, 1944, Serial No. 562,334

This invention relates to electron discharge devices.

Heretofore in devices of the aforesaid general type, in which shields are provided between the ends of the cathode and the inner wall of the envelope to prevent projection of electron beams outwardly from the cathode toward the envelope, said shields have been supported at one point only, such single point of support being usually at the edge of the shield. This arrangement has proven satisfactory if the device be not exposed to influences that may cause a change of position of the shield. The shields in question are quite thin and under certain conditions they are easily displaced. In magnetrons, for example, wherein the magnetic attraction of the magnet poles upon the interior structure is considerable, it has been found that the aforesaid magnetic attraction tends to tilt such shields about their single point of support, thus varying the tuning of the device. In fact the displacement of the shield may be enough to bring the shield into such close proximity to other parts as to cause short-circuiting.

One of the objects of the present invention is to provide a device in which displacement of a shield, due to magnetic attraction or other causes, is precluded.

In electron discharge devices of the general type referred to, it has also been found that other parts may be unfavorably affected by the afore' said magnetic attraction. It has been found, for example, that in the type of electron discharge devices employing an indirectly-heated cathode, the effect upon the wound heater wire may be detrimental to the proper operation of the device.

Another object of the present invention is to neutralize the effect of the magnetic attraction of the heater-wire, thus eliminating any objectionable eiect from this cause.

A further object of the present invention is to provide an improved shield for preventing electron beams from being projected outwardly toward the envelope of the device.

These objects and such other aims and objects as may hereinafter appear will be best understood from the following description, taken in connection with the accompanying drawing of one embodiment of the invention herein presented for illustrative purposes.

In the drawing:

Fig. 1 is a vertical section through an electron discharge device embodying one illustrative em-l bodiment of the invention;

2 Claims. (Cl. Z50-27.5)

Fig. 2 is a cross-section on line 2--2 of Fig; 1; Fig. 3 is an enlarged vertical section of the cath.. ode on line 3--3 of Fig. 4, showing the connection of the upper lead-in conductor to the upper end of the rod supporting the heater-wire and to the protective disc between the upper end of the cathode and the top cap of the device; it also shows the heater-wire in elevation; and Fig. 4 is a cross-section on line 4-4 of Fig. 3,v` showing the connection of the lower lead-in conductor to the protective disc between the bottom cap of the device and the lower end of the cathode.

The invention is herein illustratively shown and described in itsl application to that type of 'elec-J tron discharge device known as a magnetron.

The illustrative embodiment of the present invention shown comprises a cylindrical envelope 2,' hermetically sealed at both ends by caps 4 and 6.' Said envelope and caps may and preferably will be made of copper. Upon the inner surface of said envelope there is provided a central, circular projection 8 to which are soldered a plurality of suitably spaced, radially disposed plates lll, the inner ends of which constitute anode faces. Said plates I0 will preferably be stamped from a sheet of highly conductive copper. Said anode faces cooperate with a cathode l2 supported substantially centrally of said anode faces, said cathode being preferably of the indirectly-heated, thermionic type, and comprising a conductive sleeve I4 of nickel or other suitable conductive material coated with a coating of barium 'and strontium oxide or other suitable electron-emissive material.

The vcathode l2 contains a helically wound insulated heater-wire I6 (see Fig. 3) supported by a conductive rod I8, the opposite ends of which are mounted in insulating washers 2l), 24 in the opposite ends respectively of said sleeve I4. In accordance with the present invention said helically wound heater-wire I6 is wound clockwise throughout a part of its length and contra-clockwise throughout another portion of its length (see Fig. 3)'. Herein the winding in one direction is equal to that in the opposite direction. This'- serves to neutralize the objectionable effect of the magnetic field generated by the heater-wire, by causing it to be exerted in one direction by one half of the wire and in the opposite direction by the other half so that diversion of the magnetic end of said heater-wire is electrically connected to said supporting rod I8, the other end of said heater-wire being electrically connected to the conductive cathode sleeve I4.

A lead-in conductor 26 is sealed through a glass seal 28 mounted at the outer end of a conducting pipe 3i! which extends through the wall of said envelope 2 and is hermetically secured therein adjacent the lower end thereof. A secondlead-in conductor 32de sealed througha-.similar glass seal 34 mounted at the outer end of .a -conducting pipe 36, also hermetically secured in the wall of said envelope 2 at the upper end thereof.

Light, protective shields 38 and 40, respectively, of tantalum or other suitable material are provided between the upper end of :the Y:cathode L2 and the envelope cap 4, andbetween .thelower end of said cathode I2 and the envelope-capiti.

These shields prevent electroni-beams from beingA projected outwardly from said cathode toward said two envelope caps 4 and 6. The edges vof the thin shields heretofore used for this purpose were rough and relatively sharp, which were liable to causesparking. contemplates the provision of means .for preventingsuchsparking. In accordance with the present invention'this isc'onveniently accomplished by welding a metal ring 42 to the marginal portion fof one side of the shield substantially as shown in Fig. 3, thus increasing the thickness of the edgesurface. Said ring'42 Yalso serves 'the further-useful purpose of reinforcing the'thin shield and rendering it more rigid.

In the illustrative Aembodiment. vof ,theinvention shown in the drawing, the lcad-inconductor 32 is connected to said shield 38'by.abracket or .support consisting `or "a conductive wire bent backupon itself :at 44 (see Fig. 2) so as ftofform two substantially parallel arms #46, eachpres'enting a LJ-shaped formation 48 and a lesser U' shapedormation 59, the latter also substantiaily parallel to'each other but in planes 4at right angles tothe plane of the U-shapedformations 48, and between the .latter yand the bend 444. 'The -free endsofthetwo arms 45 are welded vto the'lead-in conductor 32 and said arms are also welded at the;,pointsr52 (see Fig. 2) tothe reinforced edge of-the shield on the underside of the latter, the bend 44 of said armsbeing welded to the opposite edge of said shield egt-54 (see Fig. 3). The lesser U-shape'd formations arefwelded to opposite sides of the upper end of theaforesaid heater-wire it supporting rod I8 projecting from the upper endof the cathode I2, thus electrically connecting said lead-in wire 32 to said heaterwire I6. The lesser U-shaped formations Siiprovide :the required spacing of said wire arms 46 and said'shield 38 from theitop oftheycathode l2.

`Thelower shield 401s electrically connected to the cathode sleeve .I4 bymetal'supports' welded tothe" lower edge of said cathode and to thereinforced edge of said shield 4a, ysaid shield being in.

turnconnected'to the lead-in conductor 2S by-two wirearms and 60 having one end welded to said lead-in vconductor and the Aother end welded to rThe present invention thereinforcededge of said shield 4i). These `wire 4 end of the heater-wire supporting rod I3, on the one hand, and the lead-in conductor 25 with said shield 4U and the cathode I2, on the other hand, provide the necessary electrical connections of said two lead-in conductors with said heaterwire and with the cathode, it having already been stated above that one end of said heater-wire IS is .electrically connected to said `rod I3 and the other end .ofV said heater-wire is connected to said cathode sleeve I4.

A coupling loop 64 extends into the space between two of said plates IU, one end of said loop being connected to the inner end of a conductjingpipe herrnetically sealed through the wall o'f'th'e Ierivelopei, substantially midway between the1endsthereof,the other end of said loop being lconnected toa conductor 68 extending through said pipe '66' and sealed through a glass seal li) fat the louter end of said pipe 6B. An additional conducting pipe, not shown, may be electrically connected to saidpipe 66 to form with said conductor 68 a concentric line through which the high-frequency oscillations generated by the device when it is energized and placed between magnetic poles .'I2 and 14 may be conducted to a suitable utilizingv circuit.

The firm support for the shield provided by welding the wire vsupport; to the shield at a plurality of points, forv example three suitably spaced points 52, E2 and 54, precludes any buckling, bending, tilting or other displacement of said shield from any cause.

Asfalready pointed out, the shields of tantulum or any other suitable materialmay be used. For some casesnickel is particularly desirable, but owing to its liability to distortion in a magnetic eld, shields of this metal have'heretoiore not proven very satisfactory. The rm support afforded the shields by the present invention, hcwever, has overcome this dlliculty and made the use of nickel shields not only perfectly feasible but Adesirable in certain cases.

The above-described connections also, while affording a sturdy and reliable support for the cathode by said lead-in conductors, do not objectionably affect the temperature of the cathode, for while a certain amount of heat will be withdrawn from the cathode by the shields, the amount so withdrawn in the present instance is an Yadvantage, it being neither too little nor too muc-h.

Thepresent invention enables shields 38 and 40, and the wire supports for the latter, to be assembled and welded in their proper positions to the cathode Ystructurebefore the cathode is placed inthe tube. The operator can thus make sure that the shields and other parts are correctly assembled and properly positioned before placing the assembly in the tube. The welding of the free ends of the wire supports to the ends of the lead-in wires is all that remains to be done and this can be accomplished without any risk of disturbing the assembly in the tube. The shields are supported in such manner that any change from the position in which they have been adjusted before .being placed yin the tube is practically impossible, whether by magnetic attraction or any other causes. The same applies to the heaterwire, the windin-g of which in opposite directions neutralizes any effect the magnetic eld created by said wire might have upon that of said pole pieces and precludes any displacement of said heating wire by vmagnetic attraction by said pole pieces.

It will be noted that the coils of the resilient heater-wire are in close contact with the interior lateral wall of the cathode. It will also be noted that the last coil of the closely coiled wire at one end rests against the disc 2l welded to the inner surface of the cathode and carrying the ribbons 23 that hold the insulating washer 24 in place, and that the last coil of said heater-wire at the other end of the coiled wire rests against the disc 55 welded to the inner surface of the cathode. The closely coiled heater-wire I6 is thus braced both longitudinally and transversely within the cathode and cannot be displaced whatever the position of the cathode may be, whether vertical or horizontal, and the coils of said heater-wire are distributed uniformly throughout the length of the cathode, thus ensuring even heating of the cathode throughout its length.

Wherever the term a plurality is used it is to be construed as meaning two or more.

I am aware that the present invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and I therefore desire the present description to be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the aforesaid description to indicate the scope of the invention.

What is claimed is:

1. An electron discharge device comprising an itself forming two substantially parallel arms. y

each provided at the same distance from the free end of said arms with a U-shaped formation, said U-shaped formations extending in same direction at right angles to the planeA of said arms, the free end portions of said arms being welded to said lead-in conductor, the closed end of said support and said U-shaped formations being welded to the marginal portion of said shield. HOMER G. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 'Number Name Date 2,408,239 Spencer Sept. 24, 1946 2,406,277 Bondley Aug. 20, 1946 1,758,833 Hendry May 13, 1930 1,287,265 Dushman Dec. 10, 1918 1,872,010 Robinson Aug. 6, 1932 1,790,286 Sperti et al Jan. 27, 1931 2,311,658 Hansen et al. Feb. 3, 1943 2,163,157 Samuel June 20, 1939 Certificate of Correction Patent No. 2,439,786. April 20, 1948. HOMER G. ANDERSON It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows; Column 5, line 35, for the Words points of read points on; line 36, for one on read one of and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofloe.

Signed and sealed this 8th day of June, A. D. 1948.

[SEAL] THOMAS F. MURPHY,

Assistant Oom/missioner of Patents. 

